This invention relates to fuel cells and, in particular, to fuel cells having carbonate as the electrolyte.
In carbonate fuel cells of conventional design, carbonaceous fuel is provided to the fuel cell anode compartment for the required anode reaction. At the cathode compartment, oxidant or air and carbon dioxide are supplied for the cathode reaction.
The carbon dioxide supplied to the cathode compartment is typically generated from the anode exhaust which includes steam, carbon dioxide carbon monoxide and hydrogen. Conventionally, this exhaust is coupled to a burner where the hydrogen and carbon monoxide is combusted with the air to generate carbon dioxide. The resultant carbon dioxide and other components of the combusted products are then coupled to the inlet manifold of the cathode compartment.
This technique of generating and recirculating carbon dioxide to the cathode compartment of the fuel cell results in an efficient fuel cell power plant. However, there is a significant cost associated with the external burner and with the high temperature stainless steel piping required to recycle the resultant combusted gases. This has prompted researchers to consider proposals which increase the efficiency of the process and/or reduce the piping required.
One proposal involves increasing the burner efficiency by utilizing a catalytic burner. A second proposal also utilizes a catalytic burner, but contemplates placing the burner within the cathode inlet manifold. While these proposals offer certain improvements, the first proposal still requires that expensive piping be used for the combusted gases. The second proposal, while reducing the piping, does so at the expense of increasing the complexity of the cathode inlet manifold.
It is therefore a primary object of the present invention to provide a carbonate fuel cell and method with improved generation and delivery of carbon dioxide gases to the cathode compartment of the fuel cell.
It is a further object of the present invention to provide a carbonate fuel cell and method in which carbon dioxide from the anode exhaust gas is generated and supplied to the cathode compartment of the fuel cell without a burner external of the fuel cell and without external piping.